Heat exchanger



Jan. 26 1926. 1,570,674

B. M. JOHNSON HEAT EXCHANGER Filed Feb. 9 1924 2 Sheets-Sheet 1 ooooo'oooooooggoo o Jan. 26 1926.

B. M. JOHNSON HEAT EXCHANGER Filed Feb. 9, 1924 2 Sheets-Sheet 2 INVENTOR Patented Jan. 26, 1926.

,UNITED STATES PATENT OFFICE.

BOYD I. JOHNSON, -METUCHEN, NEW JERSEY, ASSIGNOR TO THE GABBORUNDUM.

COMPANY, OF NIAGARA FALLS, NEW YORK, ACORPORATION OF PENNSYLVANIA.

HEAT EXCHANGER.

To all whom it may concern."

Be it known that I, Born M. JOHNSON, a citizen of the United States, residing at Metuchen, county of Middlesex, and State changers of the type adapted for transferring heat from live gases ofcombustion to air or other fluids. The purpose of the present invention is to enable the use of the high temperature silicon carbide radiating combustion chamber in a heat exchanger constructed mainly of materials having a comparatively low heat resistance. This purpose is accomplished by protecting the -metal sheets and tubes which constitute the main bodv of the heat exchanger from the direct radiation of heat from the walls of the combustion chamber by means of silicon carbide tubes interposed between the metal tubes and the walls of the combustion chamber and a fire-clay wall forming arefractory lining for a portion of the metal walls of the heat exchanger.

Since thin metal sections will transmit heat more readily than heavy refractory materials, a' very efficient heat exchanger is thus obtained by combining the possibilities for eflicient combustion in the silicon carbide radiating combustion chamber with the high heat conductivity of silicon carbide in the tubes next to the chamber and the higher .heat conductivity of the met-a1 tubes and 1 P sheets. This efliciency is obtained with a comparatively low cost of construction due to the use of metal sheets and tubes through- -out the main body of. the heat exchanger.

A preferred embodimentpf the invention is-shown in the accompanying drawings, 1n which Figure 1 is a sectional plan view of the heat exchanger, the sectlon being taken on the line'I -I of Figure 2;

Figure 2 s a longltudinal vertical section I on the line 11 11 of Figure 3;

Figure 3 is a transverse vertical section on the line III-III of Figure 2;

Figure 4 is. a detail VIGW'Of the silicon carbide radiating combustion chamber, and

Application filed February 9, 1924. Serial No.'691,576.

Figure is a detail of cooperating refractory elements for supporting the silicon carbide tubes. 7

In the illustrated embodiment of the invention, the heat exchanger comprises an outer shell 2 formed of spaced metal walls having some suitable heat insulating material 3 filling the space therebetween. An oif-take 4 for the heated air communicates with the space within this outer shell through a side thereof, while an in-ta-ke 5 for the cold air communicates with such space through an opening in a metal plate 6 which forms the closure for the rear end of the shell.

Within the outer'shell 2 is an inner 'metal shell 7, the top, side and end walls of which are spaced from the top, side and end walls of the outer shell. The lower portion of the inner shell is protected by an inner fireclay wall 8 forming a refractory lining for such lower portion and encloslng a space within which is placed a silicon carbide radiating combustion chamber 9. This chamber is of vU-shape and communicates at one end with the exterior of the heat exchanger through an opening 10 in the front end poropening 10 forms the burner opening for the combustion chamber, this chamber being providedat the other end of its U-shaped assage with an outlet 0 ning 11 through which the gases of com ustion pass from the combustlon chamber into the inner shell. The combustion chamber is s aced from the floor of the heater by a suitable fire-clay base12 which is provided with spaces 13 to permit thecirculation of the gases of combastion between the base and the lower wall of the combustion chamber.

Directly above the top wall of the com bustion chamber is arranged a row of silicon carbide tubes 14, and another row of silicon carbide tubes 15 is arranged opposite the rear end wall of the combustion chamber. These silicon carbide tubes 14 and 15are supported at their ends in the side portions of the fire-clay'wall 8 and in the slde walls of the inner shell 7, said fire-clay wall being composed, in part, of bricks 16 of the form shown in Figure 5. These bricks have cooperating recesses therein forming circular openings for receiving the ends of the tubes. Above the silicon carbide tubes 14 are placed banks of metal tubes 17, sup ported at their ends in the side walls of the inner metal shell 7 and communicating with the spaces between these side walls and the,

side walls of the outer shell. Another row of metal tubes 18 is interposed between the silicon carbide tubes 15 and the rear end portion of the fire-clay wall 8, these tubes being supported in the side ortions of said wall and in the side Walls 0 the inner shell in the same manner as the tubes 14 and 15. Within the inner shell are horizontal metal baflies 19 which compel the gases of combustion, after they emerge from the opening 11, to make several passes the full length of the inner shell before assing out of the heat exchanger through the off-take flue 20. This flue is located at the rear end of the heat exchanger while the outlet 11 from the combustion chamber is located at the front end of the heat exchanger. The flue 20 has the same width as the inner shell and is located in the space between the rear end wall 6 of the outer shell and the rear end wall 21 of the inner shell and spaced from both of these walls. The rear end wall 21 and the top Wall of the inner shell extend beyond the side walls of the latter to the side walls of the outer shell, so that the air entering through the intake. 5 is compelled totravel I upwardly to the space between the top wall of the inner shell and the top wall of the outer shell, then to travel to the front end of the heater into the space between the front end wall of the inner shell and the front end wall of the outer shell.- Baflles 22 between the side walls of the inner shell and the side walls of the outer shell are so arranged that the air, after entering the space between the front end wall of the inner shell and the front end wall of the outer shell, is compelled to make several passes the width of the inner shell through the tubes 14, 15, 17 and 18 before it can finally pass out of the heat exchanger through the off-take 4.

The walls-of the inner shell and the baffles 19 which direct the flow of the gases of combustion through the inner shell will, preferably, be constructed of calorized metal plates built up in sections and bolted with calorized bolts. The tubes 18 and the tubes 17 in the lower banks may also be made of calorized metal since they are subjected to higher temperatures than the tubes 17 in the upper banks. The tubes 17 in the upper banks may be made of ordinary iron or steel.- If the heat exchanger is to be operated at very high temperatures, all of the metal tubes may be made of calorized metal,

whereas, if the heat exchanger is to be operated at relatively low temperatures, all of the metal tubes may be made of ordinary iron or steel.

It will be apparent that the heat is supplied to the heat exchanger both in the form of radiant heat from the silicon carbide radiating combustion chamber and alsoby the sensible heat in the gases of combustion emerging from the combustion chamber. These gases, as they emerge from the combustion chamber, are directed by the baflies 19 so that they are compelled to make several passes the length of the inner shell before passing to the stack through the OE- take flue 20. In their travel through the inner shell in this manner they are in con tact with the banks of tubes which carry the air to be heated. After making the last pass through the inner shell they then pass through the oif-take flue 20 which is surrounded by the air entering the heat exchanger through the intake 5. The air to be heated passes around the ofl-take flue 20, over the top of the inner shell, down through the space between the front end wall of the inner shell and the front end wall of the outer shell and then makes several passes the width of the inner shell through the tubes which are surrounded by the hot gases of combustion. The air in its travel through the heat exchanger may pass through any of the tubes of the bank composing each pass. The silicon carbide, steel and/or calorized metal tubes of the bank composing each pass all discharge into a common chamber, that is, the chamber 23 or the chamber 24 (Figure 1). Upon such discharge, due to natural convection currents, the air which has been heated the most in the lower and hotter tubes changes position with the relatively cooler air which has passed through the upper tubes. This means that on the next pass cooler air enters the hot tubes than would be the case if all the tubes of the bank composing a pass did not discharge into a common chamber. The same thingoccurs in each successive pass, the general temperature of the air being raised but no local hot 4 spots developing. Air is continually in motion in the spaces between the inner and outer walls of the heat exchanger, which sible to utilize to the maximum extent the This ' but they also further protect the metal tubes by absorbing a portion of the heat contained in the gases of combustion before these gases come in contact with the metal tubes. The arrangement whereby the silicon carbide, steel and/or calorized metal tubes of the bank composing each pass discharge into a common chamber is particularly adaptable for a heat exchanger from. which a large volume of air at a comparatively low temperature is desired, and enables a high temperature heating medium to be employed without overheating any portion of the heat exchanger. Since the effective temperature on any of the tubes is the average of the surrounding gas temperature and theinner air temperature, the lower tubes would be continually at a much higher average temperature than results with the arrangement of the present invention were the mixing chamber at the end of each pass omitted.

While I have shown and described a preferred embodiment of the invention, it will be understood that changes may be made in the details of construction shown without departing from the spirit of .the invention or scope of the appended claims. It will also be understood that the invention is not limited in its use to heating air.

I claim:

1. A heat exchanger, comprising. a radiating combustion chamber, metal heat transfer means arranged adjacent said chamber, independent refractory. heat transfer means interposed between said combustion chamber and said -metal heat transfermeans asa battle to partially protect the metal heat transfer means from'direct radiation of heat from said combustion chamber, and means for conducting the medium to be heated combustion therewith, and means through said exchanger in contact with one surface of said metal and refractory heat transfer means, substantially as described.

2. A heat exchanger, comprising a radia ting combustion chamber, metal heat transfer-means arranged adjacent said chamber, independent refractory heat transfer means interposed between said combustion cham--- her and sald metal heat transfer means as a baffle to partially protect the metal heat transfer means from direct radiation of heat from said combustion chamber, all of said heat transfer means being adapted to be heated also by direct contact of'the ases of or conducting the medium to be heated through means, substantially as described;

said exchanger in contact with one surface of said metal and refractory. heat transfer supported in said shell, a radiating combus tion chamber within said shell havinga silicon carbide radiating Wall, and a plurality of independent silicon carbide conductin tubes interposed between said wall and said metal tubes as a bafile to partially rotect the latter from direct radiation of eat from said wall, all of said tubes being adapted to be heated also by direct contact of the gases of combustion therewith, substantially as described.

5. A heat exchanger, comprising a metal shell, a plurality of metal conducting tubes supported in said shell, a combustion chamber within said shell adapted to heat said tubes by direct contact of the gases of combustion therewith and having-a silicon carbide radiating wall, a. refractory wall interposed between said chamber and a portion of said shell, a plurality of silicon carbide conducting tubes interposed between said radiating wall and said metal tubes and supported by said refractory wall, and means for conducting the medium to be heated through all of said tubes, substantially as described.

Y 6. A heat exchanger, comprising an inner metal shell, an outer metal shell surrounding-and-"spaced from said inner shell and having an inlet and an outlet for the medium to be heated, a plurality of metal tubes supported in said inner shell and communicating with vthe spaces between the inner and outer shells, a combustion chamber within said inner shell adapted to heat said tubes by direct contact of the gases of combustion therewith and having a silicon carbide radiating wall, and a plurality of silicon carbide conducting tubes'interposed between I dium to be heated through said exchanger in contact with one surface of said metal and silicon carbide heat transfer means, substantially as described.

'8. A heat exchanger, comprising metal conducting tubes and silicon carbide conducting tubes, the silicon carbide tubes being separate from the metal tubes, means for directing hot gases through said exchanger in contact with one surface of said tubes in such manner that the silicon carbide tubes absorb a portion of the heat contained in such gases before they come into contact with the metal tubes,'and means for directing the medium to be heated through said exchanger in contact with the opposite surface of said tubes, substantially as described.

9. A heat exchanger having a passage therethrough for hot gases of combustion,

-metal.conducting tubes and silicon carbide conducting tubes arranged in said passage, the silicon carbide tubes being separate from the metal tubes and arranged to absorb a portion of the heat contained in the gases before they reach the metal tubes, and means for conducting the medium to be heated through said tubes, substantially as described.

10. A heat exchanger, comprising outer metal Walls, inner metal walls spaced from said outer walls, independent, metal and silicon carbide conducting tubes supported in said inner walls and communicating with the spaces between the inner and outer metal walls, means for directing the medium to be heated through the tubes and the spaces between the inner and outer walls, and means for directing hot gases of combustion through the heat exchanger first in contact with the silicon carbide tubes and then in contact with the metal tubes, substantially as described.

11. A heat exchanger, comprising an inner metal shell, an outer metal shell having its walls spaced from the Walls of the inner shell, metal and silicon carbide conducting tubes supported by the inner shell and communicating with the spaces between the inner and outer shells, a combustion chamber within the inner shell and adapted to heat said tubes by direct contact of the gases of combustion therewith and having a silicon carbide radiating wall, the silicon carbide tubes being arranged between said radiating wall and the metal tubes, :1 metal off-take flue leading from said inner shell, and an intake flue for the medium to be heated completely surrounding said ofi-take flue and leading to the spaces between the inner and outer shells.

12. A heat exchanger, comprising a plurality of banks of conducting tubes each composed in part of silicon carbide and in part of independent metal tubes, a mixing chamber between the discharge ends of the tubes of each bank and the intake ends of the tubes of the next bank, and means for directing hot gases through said heat exchanger to heat such tubes, the construction and arrangement being such that the silicon carbide tubes are subjected to higher temperatures than the metal tubes, substantially as described.

13. A heat exchanger, comprising a plurality of banks of conducting tubes arranged side by side and each composed in part of silicon carbide and in part of independent metal tubes, baffle means for compelling the medium to be heated to make a pass through the tubes of one bank in one direction and then through the tubes of the next bank in the opposite direction, a mixing chamber between the discharge ends of the tubes of each bank and the intake ends of the tubes of the next bank, and means for directing hot gases through said heat exchanger to heat such tubes, the construction and arrangement being such that the silicon carbide tubes are subjected to higher temperatures than the metal tubes.

14. A heat exchanger, comprising a radiating combustion chamber having a silicon carbide radiating wall, a plurality of banks of conducting tubes arranged side by side above said Wall and each composed of metal tubes and independent silicon carbide tubes arranged between said wall and the metal tubes, means for directing the gases of'combustion in contact with said tubes in such manner as to subject the silicon carbide tubes of each bank to'the higher temperatures,. and a mixing chamber between the discharge ends of the tubes of each bank and the intake ends of the tubes of the next bank.

In testimony whereof I have hereunto set my hand.

BOYD M. JOHNSON. 

